Blood analysis systems and methods

ABSTRACT

Blood typing systems and methods are provided. In one embodiment, the method may be achieved by applying a sample to a surface of a substrate having one or more binding agents immobilized thereon, wherein the one or more binding agents are capable of binding to one or more substances in the sample; substantially removing unbound material from at least a portion of the substrate having immobilized binding agent; and detecting substances bound to the one or more binding agents immobilized on the substrate; wherein the applying the sample to the surface of the substrate step is concurrent with the removing unbound material from at least a portion of the substrate step. Systems and other methods are also described and illustrated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 15/543,579, filed Jul.14, 2017, now U.S. Pat. No. 10,732,189, which is the U.S. national stageapplication of International Patent Application No. PCT/IB2016/050157,filed Jan. 14, 2016, which claims the benefit of U.S. Provisional PatentApplication No. 62/107,114, filed Jan. 23, 2015.

FIELD

This disclosure relates generally to analysis of patient samples such asblood samples.

BACKGROUND

Millions of people donate their blood each year. Before the blood fromthe donor can be transfused into a recipient, the blood must be typed.Typically, the blood is tested for ABO and RH1 (Rhesus D antigen) bloodgroups and is screened for alloimmune antibodies of clinicalsignificance. To determine the blood group, red blood cells (RBCs orerythrocytes) are reacted separately with anti-A, anti-B, anti-AB andanti-D antibodies. This type of test is known as antigen typing (e.g.,grouping and phenotyping). The serum/plasma from the same blood sampleis also individually tested with Type A and Type B reagent RBCs and atleast two different Type O reagent cells representing most of theantigens of clinical significance. The type of test with Type A and TypeB reagent RBCs is known as reverse typing and the type of test with TypeO reagent cells is known as antibody screening.

More than 150 million tests are performed annually in blood centers todetermine the blood groups as well as antibodies of clinicalsignificance in the serum/plasma. Generally, transfusion of blood isrequired in emergency situations for which it is desirable to determinethe compatibility between the donor and recipient in as short a time aspossible. An automated high-throughput system and method of blood typingis therefore desired that can test multiple samples at once and that canprovide quick test results. Additionally, needing less blood sample fromthe patient is also desirable.

SUMMARY

In an embodiment, a method is disclosed in which the presence or absenceof a substance in a sample is determined. The method comprises applyinga sample to a surface of a substrate having a binding agent immobilizedthereon, wherein the binding agent is capable of binding to a substancein the sample; removing unbound material from at least a portion of thesubstrate having immobilized binding agent; and responsive to detectingthe substance bound to the binding agent immobilized on the substrate,identifying the substance present in the sample; and responsive to notdetecting the substance bound to the binding agent immobilized on thesubstrate, determining that the substance is absent in the sample;wherein the applying the sample to the surface of the substrate step isconcurrent with the removing unbound material from at least a portion ofthe substrate step. The applying a sample to the surface of thesubstrate and the removing unbound material from at least a portion ofthe substrate steps may be performed with a hydrodynamic flowconfinement dispenser. In an embodiment, the hydrodynamic flowconfinement dispenser is a microfluidic probe. In an embodiment, thehydrodynamic flow confinement dispenser is a microfluidic probe havingmultiple microchannels. In another embodiment, the hydrodynamic flowconfinement dispenser is an array of microfluidic probes.

In some embodiments, a system for determining the presence or absence ofa substance in a sample includes a substrate having a binding agentimmobilized in a discreet location, wherein the binding agents arecapable of binding to a substance in a sample; a dispenser configured toconcurrently dispense a sample onto the substrate and to remove unboundmaterial from the substrate; a light source configured to illuminate thesubstrate; and a detector configured to detect the presence or absenceof the substance bound to the binding agent.

Further disclosed herein are blood analysis systems and methods of usingthese systems to analyze blood samples. More particularly, thedisclosure relates to systems and methods for detection of erythrocytegroup and phenotype (antigen typing), for screening and identificationof typical anti-erythrocyte antibodies reverse typing and atypicalanti-erythrocyte antibodies (antibody screening), for the determinationof the compatibility between a donor and a recipient (cross-matching)and for the demonstration of erythrocytes coated with antibodies and/orwith activated serum complement fractions (e.g., Direct AntiglobulinTest).

In some embodiments, the hydrodynamic flow confinement dispenserincludes structures for separation of plasma from red blood cells in awhole blood sample. In an embodiment for separating red blood cells fromplasma, the microchannel has a diameter of less than 6 micrometers. Insome embodiments, the diameter is less than 4 micrometers or less than 2micrometers or 1-2 micrometers. The cross section of the microchannelmay be any appropriate shape including rectangle, square, circular, ovaland elliptical or a combination of those.

In some embodiments, the surface of the substrate is wet. In anembodiment, the applying a sample to the surface of the substrate stepcomprises dispensing one or more samples each in at least one discreetpath. In certain embodiments, the path is a straight line. In someembodiments, the path is from about 25 nanometers to about 500micrometers wide. In an embodiment, the applying a sample to the surfaceof the substrate step comprises dispensing one or more samples each inat least one discreet spot. In some embodiments, the at least onediscreet spot is from about 25 nanometers to about 500 micrometers indiameter. In some embodiments, the sample is selected from a groupconsisting of whole blood, red blood cells, plasma, serum and saliva.

In an embodiment, the one or more binding agents comprise one or moreantibodies, or fragments thereof, or some specific lectins, to red bloodcell antigens and the substance in the sample detected is the red bloodcell antigens.

In another embodiment, the one or more binding agents comprise one ormore native or hemolyzed phenotyped red blood cells, chemicallysynthesized polypeptide and polysaccharide blood group antigens,recombinant red blood cell antigens or red blood cell membrane extractsand the substance is one or more antibodies, or fragments thereof, tothe red blood cell antigens, the recombinant red blood cell antigens orred blood cell membrane extracts.

In yet another embodiment, the binding agent is a multi-part bindingagent. The first portion deposited on the substrate comprises lectins orone or more antibodies, or fragments thereof, to red blood cellantigens. The antibodies are universal antibodies to red blood cells.The second part of the binding agent deposited on the substrate arephenotyped or non-phenotyped red blood cells from a potential blooddonor and are bound to the binding agent. The substance is plasma from apatient in need of a blood transfusion and antibodies, or fragmentsthereof in the patient plasma bind to the red blood cells from thedonor.

In yet another embodiment, the one or more binding agents comprise oneor more antibodies, or fragments thereof, to human immunoglobulinsand/or activated serum complement fractions and the substance is redblood cells coated with antibodies and/or with activated serumcomplement fractions.

In some embodiments, the one or more binding agents are immobilized indiscreet lines. In some embodiments, the one or more binding agents areimmobilized in discreet spots. In some embodiments, 1-100 binding agentsare bound to the surface of the substrate.

A system for antibody screening, antigen typing (including DirectAntiglobulin Test) and cross-matching, the system comprising a substratehaving a binding agent immobilized in discreet locations, wherein thebinding agent is capable of binding to a substance in a sample; adispenser configured to simultaneously dispense the sample onto thesubstrate and to remove unbound material from the substrate; a lightsource configured to illuminate the substrate; and a detector configuredto detect the presence or absence of the substance bound to the bindingagent.

In some embodiments, a system for cross-matching includes a substratehaving donor red blood cells immobilized in discreet locations thereon;a dispenser configured to dispense donor red blood cells and/or patientplasma onto the substrate and to simultaneously remove unbound donor redblood cells or an unbound portion of the patient plasma from thesubstrate; a light source configured to illuminate the substrate; and adetector configured to detect the presence or absence of antibodiesbound to the donor red blood cells.

Item 1. A method of determining the presence or absence of a substancein a sample, the method comprising:

-   -   applying the sample to a surface of a substrate having a binding        agent immobilized thereon, wherein the binding agent is capable        of binding to the substance in the sample;    -   removing unbound material from at least a portion of the        substrate having immobilized binding agent; and    -   responsive to detecting the substance bound to the binding agent        immobilized on the substrate, identifying the substance present        in the sample;    -   and responsive to not detecting the substance bound to the        binding agent immobilized on the substrate, determining that the        substance is absent in the sample;    -   wherein the applying the sample to the surface of the substrate        step is concurrent with the removing unbound material from at        least a portion of the substrate step.

Item 2. The method of Item 1, wherein the applying the sample to thesurface of the substrate and the removing unbound material from at leasta portion of the substrate steps are performed with a hydrodynamic flowconfinement dispenser.

Item 3. The method of Item 2, wherein the dispenser is a microfluidicprobe.

Item 4. The method of Item 3, wherein the dispenser is a microfluidicprobe having a plurality of microchannels.

Item 5. The method of Item 3 or 4, wherein the dispenser is an array ofmicrofluidic probes.

Item 6. The method of any one of previous Items 3 to 5, wherein thedispenser is a microfluidic probe having a microchannel that excludesred blood cells based on size.

Item 7. The method of Item 6, wherein the microchannel includes a crosssection having a diameter of less than 6 micrometers.

Item 8. The method of Item 6, wherein the microchannel includes a crosssection having a diameter of less than 4 micrometers.

Item 9. The method of Item 6, wherein the microchannel includes a crosssection having a diameter of less than 2 micrometers.

Item 10. The method of Item 6, wherein a diameter of the microchannelincludes a cross section having a diameter of 1-2 micrometers.

Item 11. The method of any one of previous Items 1 to 10, wherein thesurface of the substrate is wet.

Item 12. The method of any one of previous Items 1 to 11, wherein theapplying a sample to the surface of the substrate step comprisesdispensing one or more samples each in at least one discreet path.

Item 13. The method of Item 12, wherein the path is a straight line.

Item 14. The method of Item 12 or 13, wherein the path is from between25 nanometers to 500 micrometers wide.

Item 15. The method of any one of previous Items 1 to 14, wherein theapplying a sample to the surface of the substrate step comprisesdispensing one or more samples each in at least one discreet spot.

Item 16. The method of any one of previous Items 1 to 15, wherein thesample comprises a blood sample.

Item 17. The method of any one of previous Items 1 to 16, wherein thesample comprises a component selected from the group consisting of wholeblood, red blood cells, plasma and serum.

Item 18. The method of any one of previous Items 1 to 17, wherein thebinding agent comprises one or more antibodies to red blood cellantigens.

Item 19. The method of any one of previous Items 1 to 18, wherein thebinding agent comprises one or more native or hemolyzed phenotyped redblood cells.

Item 20. The method of any one of previous Items 1 to 19, wherein thebinding agent comprises one or more recombinant antigens.

Item 21. The method of any one of previous Items 1 to 20, wherein thebinding agent comprises one or more antibodies to red blood cellantigens and one or more native or hemolyzed phenotyped red blood cells.

Item 22. The method of any one of previous Items 1 to 21, wherein thebinding agent is immobilized in a discreet line.

Item 23. The method of any one of previous Items 1 to 21, wherein thebinding agent is immobilized in a discreet spot.

Item 24. The method of any one of previous Items 1 to 23, wherein thebinding agent is 1-50 binding agents.

Item 25. The method of any one of previous Items 1 to 24, wherein thesubstance comprises one or more antibodies to red blood cell antigens.

Item 26. The method of any one of previous Items 1 to 25, wherein thesubstance comprises one or more red blood cell antigens.

Item 27. The method of any one of previous Items 1 to 26, wherein thesubstrate is formed of at least one material selected from a groupconsisting of polyethylene terephthalate, polypropylene, polystyrene,dextran polymer, dendrimer, oligonucleotide, polycarbonate, plastic,glass, silicon, silicon oxide, metals and metal oxides, and polymerfunctionalized metals and metal oxides, PVDF, nitrocellulose, nylon andpolysulfone.

Item 28.A system comprising:

-   -   a substrate having a binding agent immobilized in discreet        locations, wherein the binding agent is capable of binding to a        substance in a sample;    -   a dispenser configured to simultaneously dispense the sample        onto the substrate and to remove unbound material from the        substrate; and    -   a detector configured to detect the presence or absence of the        substance bound to the binding agent.

Item 29. The system of Item 28, wherein the dispenser is a microfluidicprobe.

Item 30. The system of Item 28, wherein the dispenser is an array ofmicrofluidic probes.

Item 31. The method of Item 28, wherein the dispenser is a microfluidicprobe having a plurality of microchannels.

Item 32. The system of any one of previous Items 28 to 31, wherein thedispenser is a microfluidic probe having a microchannel that excludesred blood cells based on size.

Item 33. The system of Item 32, wherein the microchannel includes across section having a diameter of less than 6 micrometers.

Item 34. The system of Item 32, wherein the microchannel includes across section having a diameter of less than 4 micrometers.

Item 35. The system of Item 32, wherein the microchannel includes across section having a diameter of less than 2 micrometers.

Item 36. The system of Item 32, wherein a diameter of the microchannelincludes a cross section having a diameter of less than 1-2 micrometers.

Item 37. The system of any one of previous Items 28 to 36, wherein thesubstrate is formed of at least one material selected from a groupconsisting of polyethylene terephthalate, polypropylene, polystyrene,dextran polymer, dendrimer, oligonucleotide, polycarbonate, plastic,glass, silicon, silicon oxide, metals and metal oxides, and polymerfunctionalized metals and metal oxides, PVDF, nitrocellulose, nylon andpolysulfone.

Item 38. A method of cross-matching comprising:

-   -   applying donor red blood cells to a surface of a substrate        having a binding agent immobilized thereon, wherein the binding        agent is capable of binding to the donor red blood cells;    -   removing unbound donor red blood cells from at least a portion        of the substrate having immobilized binding agent; wherein the        applying the donor red blood cells to the surface of the        substrate step is concurrent with the removing unbound donor red        blood cells from at least a portion of the substrate step;    -   depositing patient plasma on top of the donor red blood cells;    -   removing an unbound portion of the patient plasma; wherein the        depositing a patient plasma step is concurrent with the removing        unbound portion of the patient plasma step;    -   responsive to detecting an antibody bound to the donor red blood        cells, determining that the antibody is present in the patient        plasma; and    -   responsive to not detecting the antibody bound to the donor red        blood cells, determining that the antibody is absent in the        patient plasma.

Item 39. The method of Item 38, wherein the applying donor red bloodcells, removing unbound donor red blood cells, depositing patient plasmaand removing the unbound portion of patient plasma steps are performedwith a microfluidic probe.

Item 40. The method of Item 38 or 39, wherein the donor red blood cellsare native or hemolyzed phenotyped red blood cells.

Item 41. The method of any one of previous Items 38 to 40, wherein thebinding agent comprises bound lectins or universal anti-red blood cellantibodies.

Item 42. A system for crossmatching comprising:

-   -   a substrate having donor red blood cells immobilized in discreet        locations thereon;    -   a dispenser configured to simultaneously dispense donor red        blood cells or patient plasma onto the substrate and to remove        unbound donor RBCs or an unbound portion of the patient plasma        from the substrate; and    -   a detector configured to detect the presence or absence of        antibodies bound to the donor red blood cells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a blood analysis system according to anembodiment of the invention.

FIG. 2 shows a top view of a substrate having an array of binding agentsapplied thereon in which a sample (e.g., RBCs) is applied with amicrofluidic probe according to an embodiment of the invention. Theembodiment may be used for antigen typing and the binding agents areantibodies to RBCs.

FIG. 3 shows a top view of a substrate having an array of binding agentsapplied thereon in which a sample (e.g., plasma having antibodies) isapplied with a microfluidic probe according to another embodiment of theinvention. The embodiment may be used for antibody screening and/oridentification and the binding agents are native or hemolyzed phenotypedRBCs or recombinant blood group antigens.

FIG. 4 shows a top view of a substrate having an array of binding agentsapplied thereon in which a sample (e.g., RBCs and/or plasma havingantibodies) is applied with a microfluidic probe according to anotherembodiment of the invention. The embodiment may be used for both antigentyping and antibody screening and/or identification.

FIGS. 5A and 5B show a microfluidic probe of the prior art.

FIG. 6 shows a top view of a microfluidic probe according to anembodiment of the invention.

FIG. 7 shows a top view of a microfluidic probe according to anotherembodiment of the invention.

FIG. 8 is a flow chart showing a method of applying a sample to asurface of a substrate having previously immobilized native or hemolyzedphenotyped RBCs and/or antibodies to RBCs using the system of FIG. 1according to an embodiment of the invention.

FIGS. 9 and 10 show multiple microfluidic probes in parallel connectedto a single sample or different samples according to an embodiment ofthe invention.

FIG. 11 shows a microfluidic probe having a plurality of processingliquid microchannels, which may be connected to a single sample ormultiple samples, according to an embodiment of the invention.

FIG. 12 is a flow chart showing a method of crossmatching patient plasmawith a potential donor's red blood cells according to an embodiment ofthe invention.

FIGS. 13A and 13B show results from singleplex antigen typing using amicrofluidic probe as described in Example 5A. FIG. 13B is a close upview of one of the spots shown in FIG. 13A.

FIGS. 14A-14D show results from multiplex antigen typing using amicrofluidic probe as described in Example 5B. A-positive red bloodcells bound strongly to the scanned region of the spot surface at whichthe anti-A mAb was immobilized (FIG. 14A), whereas the A-negative redblood cells did not bind at all (FIG. 14B). The D-positive red bloodcells also bound strongly to the scanned region of the spot surface atwhich the anti-D mAb was immobilized (FIG. 14C), whereas the D-negativered blood cells did not bind at all (FIG. 14D).

FIG. 15 shows results from direct antiglobulin testing using amicrofluidic probe as described in Example 6.

FIG. 16 shows results from antibody screening using a microfluidic probeas described in Example 7A.

FIG. 17 shows results from reverse ABO grouping using a microfluidicprobe as described in Example 7B.

FIGS. 18A-18B show results from cross-matching using a microfluidicprobe as described in Example 8. FIG. 18A is an image of fluorescentspots on a cross-matching slide and FIG. 18B is the measuredfluorescence intensity of each spot.

DETAILED DESCRIPTION Overview

Among all the antigenic variants of an erythrocyte membrane antigenconstituting the blood groups, more than thirty erythrocyte antigensystems have been identified to date in humans: the ABO system with theantigens A, B and H, the Rhesus (RH) system with in particular theantigens D (the absence of the D antigen being noted d), C, E, c and e,the Kell (KEL) system with in particular the two antigens K and k, theDuffy (FY) system with in particular the antigens Fy^(a) and Fy^(b), theKidd (JK) system with in particular the antigens Jk^(a) and Jk^(b), oralternatively other systems that are less commonly investigated inpractice, such as the MNS system, the Lewis (LE) system, etc.

The standard transfusion generally takes into account the groups in theABO system and the Rhesus D system (D+ ord). However, in situationswhere there is a risk of an atypical agglutinin appearing, a certainnumber of other antigens of the Rhesus system systems are taken intoaccount, in particular C, c, E and e antigens and Kell, or even othersystems.

Antibodies directed against erythrocyte antigens. Outside ofpathological situations, such as in the case of autoimmune diseases, theserum of an individual may contain two types of antibodies directedagainst erythrocyte antigens:

-   -   (i) Antibodies referred to as typical (or regular) and directed        against the antigens of the ABO system (for example, anti-A        antibody in an individual of group B).    -   (ii) Antibodies referred to as atypical (or immune), the        presence of which in the serum or plasma is circumstantial, and        which are directed more particularly against non-ABO system        antigens.        The “typical” or “regular” antibodies are more frequently        immunoglobulins of M and/or A isotype which are capable of        agglutinating red blood cells in vitro. The “atypical”, or        “irregular”, or “immune”, antibodies are most commonly of G        isotype, appearing when there is antigenic stimulation by        foreign red blood cells, for example following immunization        against one or more antigens during a blood transfusion or else        during a pregnancy due to a maternal immunoreaction directed        against the fetal erythrocyte antigens that do not belong to the        maternal blood group, in particular at the time of the birth.

Various testing used in analyzing blood includes:

ABO grouping: This analysis is the result of the combination and theinterpretation of two types of analyses: serum analyses with plasma orserum and cell analyses using the blood cell pellet (respectively areverse and forward grouping).

In the forward grouping, the individual's red blood cells are broughtinto contact with test antibodies, each having precise antibodyspecificity, directed against an antigen of the ABO system (anti-A,anti-B and anti-AB antibodies).

In the reverse grouping, the individual's serum or plasma, containingtypical circulating antibodies, is brought into contact with phenotypedred blood cells, each belonging to a precise antigenic group of the ABOsystem.

Phenotyping assay: The techniques normally used for phenotyping consist,in general, in screening for the presence or absence of the antigenbeing at the surface of red blood cell investigated, using specificantibodies.

Screening and/or identification of atypical anti-erythrocyte antibodies:This test is used to detect the presence or absence, in an individual'sblood, of antibodies directed against various erythrocyte antigens. Forthis, it is sought to demonstrate the binding of these antibodies (IgGand/or IgM) to phenotyped red blood cells, the antigens of which areknown or/and to recombinant blood group antigens. When bound onphenotyped red blood cells or recombinant antigens, these atypicalanti-erythrocyte antibodies are revealed by an anti-immunoglobulinantibody. In a first step, use is made of a panel of “screening” redblood cells (two or three red blood cells chosen so as to comprise allthe antigens of importance in transfusion for detecting (but notidentifying) the presence or absence of atypical antibodies). When thescreening is positive, the specificity of the atypical antibody orantibodies present is then identified by means of at least one panel of“identifying” red blood cells, in general comprising 10 to 15, or even20, different red blood cells phenotyped in the vast majority of theknown blood group systems.

Cross-matching assay: The objective of this analysis is to predictdonor-recipient compatibility prior to infusing a recipient with adonor's blood. This is used to confirm compatibility beyond the basictyping that is done of a donor's blood. The red blood cells originatingfrom potential donor are brought together with the potential transfusedrecipient's serum/plasma. If the potential recipient sample containsantibodies against the potential donor's red blood cells, they arerevealed with an anti-immunoglobulin antibody. Such an analysis resultsonly in the determination of the presence or absence of an antibody, anddoes not make it possible to determine the specificity thereof. Inanother type of cross-matching called “minor” cross-matching, the plasmaoriginating from the potential donor is brought together with thepotential transfused recipient's red blood cells. If the potential donorsample contains antibodies against the potential recipient's red bloodcells, the antibodies are revealed with an anti-immunoglobulin antibody.

Direct Antiglobulin Test: In particular newborns or patients sufferingfrom haemolytic anaemia or autoimmune diseases for example, the redblood cells are sensitized in vivo by antibodies or/and by serumcomplement fractions. These antibodies or activated serum complementfractions present at the surface of erythrocytes sensitized in vivo arethemselves capable of constituting antigens carried by erythrocytes andare directly detected by an anti-immunoglobulin antibody and/or ananti-complement antibody.

Described herein are systems and methods for blood analysis includingthe testing described above. The systems and methods facilitate theautomation of blood analysis. The systems and methods can be used fordetection of grouping and phenotyping, for screening and/oridentification of antibodies, cross-matching and direct antiglobulintest.

Advantages of the systems and methods described herein include, but arenot limited to: (1) providing systems that are compact in size thatdeliver nanoliter to microliter volumes of reagents and patient samples;(2) providing systems that localize the reaction chemistry and decreasereaction time; (3) providing systems capable of performing multiplexassays (e.g., testing sample from multiple patients and/or testing asingle sample for multiple analytes); (4) providing systems capable ofsimultaneous phenotyping (e.g., forward blood typing) and antibodyscreening/identification (e.g., reverse blood typing); (5) providingsystems capable of depositing native or hemolyzed red blood cells onto asubstrate while maintaining the antigenicity of the native or hemolyzedred blood cells; (6) providing systems capable of cross-matching redblood cells that may be transfused into a patient and/or (7) providingsystems in which the application of sample and washing of unboundmaterial steps may be performed simultaneously which in turn decreasesassay time.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. Thus, for example, reference to a systemcomprising “a binding agent” includes system comprising one or morebinding agents. Likewise, reference to “a substance” includes one ormore substances. As used herein, the term “about” refers to the recitednumber and any value within 10% of the recited number. Thus, “about 25”refers to any value between 22.5 and 27.5, including 22.5 and 27.5.

SYSTEMS

Referring to FIG. 1, a system 100 for analyzing blood is illustrated. Inan embodiment, the system 100 is used to phenotype (also known asantigen typing), to antibody screen and identify or to cross-match ofpatient plasma with donor red blood cells. The system 100 includes asubstrate 102, a dispenser 104 (e.g., a microfluidic probe), a lightsource 106 and a detector 108.

The substrate 102 provides a surface onto which a binding agent 110(shown in FIG. 2) is immobilized or bound. The substrate 102 isgenerally planar in shape and may be formed of one or more materialsincluding, but not limited to, polyethylene terephthalate (e.g., Mylar),polypropylene, polystyrene, polycarbonate, plastic, glass, silicon,silicon oxide, and/or metals and metal oxides either bare orfunctionalized with polymer or activated groups such as carboxyl, amine,tosyl and others. In some embodiments, the substrate is a slide formedof one or more materials including, but not limited to, polyethyleneterephthalate (e.g., Mylar), polypropylene, polystyrene, polycarbonate,plastic, glass, silicon, silicon oxide, and/or metals and metal oxideseither bare or functionalized with polymers. The substrate 102 maycontain microwells or nanowells. Examples of polymers with which tofunctionalize the surface of substrates formed from metal or metal ozideinclude glycidoxypropyltriethoxysilane, poly-L-lysine, polybrene,polyethylene glycol polymers, dextran polymer, aminopropylsilane,caroxysilane, hydrogels and polymer brushes, and/or self-assembledmonolayers of e.g. functionalized alkyl thiols, dendrimers oroligonucleotides. In an embodiment, the substrate 102 is coated withgold. In an embodiment, the substrate 102 is a microtiter plate having aplurality of wells in which the binding agents may be immobilized. Insome embodiments, the substrate 102 is a membrane formed of materialincluding, for example, nitrocellulose, polyvinylidene fluoride, nylonor polysulfone.

The surface of the substrate 102 may be wet. A wet surface is desirablein some embodiments in which the binding agents require hydration toremain active. Exemplary fluids used to wet the surface of the substrate102 include, but are not limited to, buffer, water, saline and/or oil(e.g., mineral oil).

In some embodiments, the substrate 102 is mounted on a platform that ismoveable in the X-Y- and/or Z direction.

In embodiments illustrated in FIGS. 2-4, one or more binding agents 110are bound to a surface of the substrate 102 in an array of lines. In anembodiment, the lines are about 25 nanometers to about 500 micrometerswide. In certain embodiments, the lines are about 50 nanometers to about200 micrometers wide. In some embodiments 1-100 binding agents are boundto the surface of the substrate 102. In an embodiment, the array oflines spans the width of the substrate 102. In another embodiment, thearray of lines spans the length of the substrate 102. In someembodiments, one or more binding agents 110 are bound to the substrate102 in a pattern of spots and/or dots. In an embodiment, the spots/dotsare about 25 nanometers to about 500 micrometers wide. In certainembodiments, the spots/dots are about 50 nanometers to about 200micrometers wide. In an embodiment, an array of spots and/or dots coversa surface of the substrate.

In some embodiments, a binding agent 110 is bound to the entire surfaceof the substrate 102. For example, in an embodiment in which thesubstrate 102 is a slide, the entire surface of the slide can be coatedwith a binding agent 110 (e.g., red blood cells or an antibody).

The binding agents 110 are capable of binding to one or more substancesin a blood sample (e.g., a whole blood, plasma, serum or RBC sample) ora saliva sample. In some embodiments, the binding agent 110 is anantibody to an antigen bound at the surface of a red blood cell or tohuman immunoglobulins or/and to a complement fraction (coated, e.g.,adsorbed on the red blood cells) and the substance is the antigen. Insome embodiments, the binding agent is native or hemolyzed phenotypedred blood cell or recombinant antigens and the substance is an antibodyto the antigen bound at the surface of the red blood cells. In someembodiments, the binding agent is lectin or an universal anti-red bloodcell antibody (e.g. anti-glycophorin A antibody) and the substance isred blood cells.

In some embodiments, the antibodies used as binding agents 110 orsubstances are those immunoglobulins that are specifically reactive withvarious antigenic determinants characteristic of particular bloodgroups. The antibodies may be IgA antibodies, IgM antibodies, IgGantibodies or mixtures thereof. In some embodiments, antibodies may bespecifically reactive with red blood cell antigens characterizing thevarious major and minor blood group systems. Such blood group systemsinclude, but are not limited to, the ABO system, the Rhesus (RH) systemwith in particular the antigens D (the absence of the D antigen beingnoted d), C, E, c, e and Cw, the Kell (KEL) system with in particularthe four antigens K, k, Kp^(a) and Kp^(b), the Duffy (FY) system with inparticular the antigens Fy^(a) and Fy^(b), the Kidd (JK) system with inparticular the antigens Jk^(a) and Jk^(b) , the MNS system with inparticular the antigens M, N, S and s, as well as the antigen P1 fromthe P system, the Lutheran system with in particular the antigens Lu^(a)and Lu^(b), and the Lewis (LE) system with in particular the antigensLe^(a) and Le^(b).

The antibodies may be polyclonal and/or monoclonal or a mixture ofmonoclonals or functional fragments thereof, which include the domain ofa F(ab′)2 fragment, a Fab fragment, scFv, and VHH nanobodies. Afunctional antibody fragment can be (i) derived from a source (e.g., atransgenic mouse); or (ii) chimeric, wherein the variable domain isderived from a e.g. non-human origin and the constant domain is derivedfrom a e.g. human origin or (iii) complementary determining region(CDR)-grafted, wherein the CDRs of the variable domain are from a e.g.non-human origin, while one or more frameworks of the variable domainare of e.g. human origin and the constant domain (if any) is of e.g.human origin. The antibodies can be isolated from natural source, i.e.living organism or cell culture or can be fully or partially syntheticantibodies. A synthetic antibody is an antibody having a sequencederived, in whole or in part, in silico from synthetic sequences thatare based on the analysis of known antibody sequences. In silico designof an antibody sequence or fragment thereof can be achieved, forexample, by analyzing a database of antibody or antibody fragmentsequences and devising a polypeptide sequence utilizing the dataobtained therefrom.

In some embodiments, the red blood cells used as binding agents 110 arenative phenotyped red blood cells having known blood group surfaceantigens. In other embodiments, hemolyzed phenotyped red blood cells or“ghosts” may be used as binding agents 110 or substances. Ghosts are redblood cells that have been gently hemolyzed and have their hemoglobinremoved, keeping all their antigenicity. In some embodiments, enzymetreated red blood cells may be used as binding agents 110. In someembodiments, blood group surface antigens isolated from membranes may beused as binding agents 110. In yet other embodiments, chemicallysynthesized polypeptide and polysaccharide blood group antigens as wellas recombinant blood group antigens may be used as binding agents 110.

The binding agents 110 may be deposited onto the surface of thesubstrate 102 by techniques such as, but not limited to, hydrodynamicfluid confinement, ink jet printing, spray deposition, microspottingand/or microcontact printing. During or after deposition, the bindingagents 110 may be immobilized onto the surface of the substrate 102 by,for example, electrostatic attractions, affinity interactions,hydrophobic/hydrophilic interactions, or covalent coupling.

In some embodiments, regions of the substrate 102 that do not haveimmobilized binding agents 110 and could provide non-specific bindingsites may be treated with blocking agents such as, for example, non-fatmilk protein, casein, and/or bovine serum albumin in a buffer.

In an embodiment illustrated in FIG. 2 that may be used for antigentyping or phenotyping, the binding agents 110 immobilized on the surfaceof the substrate 102 are an array of one or more antibodies each to adifferent antigen. In some embodiments, multiple antibodies to a singleantigen are immobilized on the surface of the substrate 102. Eachvertical line may represent a different antibody, e.g., anti-A, anti-B,anti-AB, anti-D, anti-C, anti-c, anti-Cw, anti-K, anti-k, anti-Kp^(a),anti-Kp^(b), anti-Fy^(a), anti-Fy^(b), anti-Jk^(a), anti-Jk^(b),anti-Le^(a), anti-Le^(b), anti-P1, anti-M, anti-N, anti-S, anti-s,anti-Lu^(a) or anti-Lu^(b).

In an embodiment illustrated in FIG. 3 that may be used for antibodyscreening and/or identification, the binding agents 110 immobilized onthe surface of the substrate 102 are an array of one or more native orhemolyzed phenotyped red blood cells, membrane extracts or/andrecombinant blood group antigens. Each vertical line represents adifferent red blood cell, for example, red blood cells RBCI, RBCII,RBCIII . . . RBCXX.

In an embodiment illustrated in FIG. 4 that may be used for antigentyping and antibody screening and/or identification (e.g., a “combo”test), more than one array of binding agents 110 (i.e., an array ofantibodies to red blood cell antigens and an array of red blood cells)may also be immobilized onto the substrate 102. For example, a verticalline each of anti-A, anti-B, anti-AB, anti-D, anti-C, anti-c, anti-Cw,anti-K, anti-k, anti-Kp^(a), anti-Kp^(b), anti-Fy^(a), anti-Fy^(b),anti-Jk^(a), anti-Jk^(b), anti-Le^(a), anti-Le^(b), anti-P1, anti-M,anti-N, anti-S, anti-s, anti-Lu^(a) or anti-Lu^(b) antibodies may bebound to the surface of the substrate 102 and a vertical line each ofred blood cells RBCI, RBCII, RBCIII . . . RBCXX may be bound to thesurface of the substrate 102.

Referring again to FIG. 1, the dispenser 104 is configured to dispense amicrofluidic or sub-microfluidic volume of one or more samples in adiscreet path on the surface of the substrate 102. In some embodiments,the path spans the length of the substrate 102. In other embodiments,the path spans the width of the substrate 102. In certain embodiments,the width of the path is from about 25 nanometers to about 500micrometers wide. In an embodiment, the dispenser 104 is also configuredto dispense one or more binding agents 110 on the surface of thesubstrate 102.

In some embodiments, the dispenser 104 is moveable in the X-Y- and/or Zdirection. Movement and functions of the dispenser 104 may be computercontrolled.

In some embodiments, the dispenser 104 is a hydrodynamic flowconfinement dispenser. In an embodiment, the hydrodynamic flowconfinement dispenser is a microfluidic probe 200 (or vertical MFP) asdescribed in U.S. patent application Ser. No. 13/881,989, which isincorporated herein. In an embodiment illustrated in FIGS. 5A and 5B,the microfluidic probe 200 may include a base layer 220, whereinprocessing liquid microchannels 223, 224 are provided together withimmersion liquid microchannels 323, 324. Each channel is in fluidcommunication with an aperture 221, 222, 321, 322, each aperture locatedon a face of the base layer (not necessarily the same face), andpreferably in close proximity. The channels 223, 224, 323, 324 alsoprovide connection between motorized pumps and the apertures 221, 222,321, 322. When moving the microfluidic probe 200 in the vicinity of asurface, processing liquid provided through the aperture 221 willcombine with the immersion liquid and preferably inserts into immersionliquid provided via the apertures 321 and 322, as symbolized by thecurved (thick) arrows if FIG. 5B. The latter are provided for the sakeof understanding; their dimension are deliberately exaggerated. In thisregard, the device is preferably configured such as to obtain a laminarflow. In some embodiments, the aperture dimensions may be a few tens ofmicrometers. The apertures are can be spaced apart by fifty micrometersor as much as hundreds of micrometers apart. As pairs of processingchannels/apertures are used herein, the processing liquid can bere-aspirated at aperture 222 together with some of the immersion liquid.Note that the flow path between apertures 221 and 222 can be inverted,i.e. processing liquid can be injected from aperture 222 while aperture221 can aspirate liquid. The processing liquid is essentially locatednearby the apertures 221 and 222 and is surrounded by an immersionliquid that is essentially present in the vicinity of the head 200. Acover layer 210 closes the channels open on the upper face of the baselayer, as depicted.

In addition, portions of the processing liquid microchannels arepreferably provided as grooves 223′, 224′ in the layer thickness of thebase layer 220, open on the upper face thereof. This way, forming amicrochannel is easily achieved, in spite of its transverse dimensions(likely small, e.g., a few tens of micrometers). After assembly, thegroove is closed by a portion of the cover layer 210. The groove may beengraved by a tool directly on the upper surface of the base layer 220.It can have any appropriate section shape, e.g. rounded, square, U or Vsection. The required tool is typically chosen according to the materialof the base layer 220. In a variant, laser ablation can be contemplated.Most advantageously yet, deep reactive ion etching (DRIE) is used forfabrication of microchannels.

As depicted in FIG. 5B, the grooves 223′, 224′ extend up to respectiveapertures 221, 222. Similarly, immersion channels 223, 224 reachrespective apertures 321, 324. In this example, channels and aperturesare symmetrically arranged around the main axis of the upper face of thehead. An aperture is directly formed at an end of the groove at thelevel of an edge 310 of the front face 320 of the base layer 220, whichhere again is easily machined. Said front end 320 is typically madeacute, which allows for compact liquid deposition on a surface ofinterest, and leaves rooms for easy optical monitoring.

Referring to FIG. 5A, vias 211, 212 are provided on the cover layer 210.An additional via 311 is shown, which allows for relaying fluidcommunication to immersion channels 323, 324 (only one via is providedhere, which feeds both immersion channels). Corresponding tubing portsconnected to the vias can be provided (not shown). The channels haveends arranged such as to face the vias.

As depicted in FIGS. 5A and 5B, the microfluidic probe 200 includes twoprocessing liquid microchannels. In some embodiments, the microfluidicprobe 200 includes more than two processing liquid microchannels. Insome embodiments, the microfluidic probe 200 may include 2-50 processingliquid microchannels (see FIG. 11). In some embodiments, themicrofluidic probe 200 may include a heating element in at least one ofthe processing liquid microchannels. Heating the sample may increase thespeed at which the antigens and antibodies react which may reduce testtime.

Exemplary processing liquids include buffer, whole blood, RBCs, plasma,serum, or oil (e.g., mineral oil). Exemplary immersion liquids includemineral oil, buffer, water, and/or saline.

In some embodiments, the microfluidic probe includes structures forseparation of plasma from red blood cells in a whole blood sample. Insome embodiments, the separation may be achieved by size and/or bycapillary forces. FIG. 6 illustrates an embodiment of a microfluidicprobe 600 having at least two processing liquid microchannels ofdiffering dimensions. The probe is configured such that it may be usedwith whole blood samples or with RBC-containing samples (i.e., RBCs inplasma) without clogging. A first microchannel 602 is sized to excludered blood cells in a whole blood sample. A second microchannel 604 issized to allow red blood cells from a sample to flow therethrough. In anembodiment in which the processing liquid microchannels have a circularcross section, the first microchannel 602 has a diameter less than 6micrometers. In some embodiments, the diameter of the first microchannelis less than 4 micrometers or less than 2 micrometers or less than 1-2micrometers. In some embodiments, the second microchannel 604 has adiameter greater than about 7 micrometers. The diameter of red bloodcells is about 6-8 micrometers. Having the larger diameter, the secondmicrochannel 604 will allow red blood cells to flow therethrough. Thecross section of the microchannel may be any appropriate shape includingcircular, oval, and elliptical. In some embodiments, inner surfaces ofthe processing liquid microchannels 602 and 604 may be coated with amaterial e.g., heparin, that prevents blood components from binding tothe inner surfaces. The whole blood sample may also be anti-coagulatedwith, for example, heparin, citrate or EDTA to prevent the blood fromclotting.

FIG. 7 illustrates an embodiment of a microfluidic probe 700 having atortuous microchannel 702 in fluid communication with a first aperture704. The diameter of the tortuous microchannel 702 is sized to retainRBCs from a whole blood sample. A smaller diameter capillary 706branches off the tortuous microchannel 702 and is in fluid communicationwith a second aperture 708. The capillary 706 allows red blood cell-freeplasma to flow therethrough.

Microfluidic probes may be formed of material that is compatible withthe fluids flowing through the channels. Exemplary compatible materialsinclude, but are not limited to, silicon, silica, polydimethylsiloxane(PDMS), gallium arsenide, glass, ceramics, quartz, polymers such asneoprene, Teflon™, polyethylene elastomers, polybutadiene/SBR, nitrites,nylon, and/or metals. The inner surface of the channels may also becoated with suitable material to reduce the affinity between the fluidcomponents and the channels themselves.

Referring again to FIG. 1, the light source 106 is configured toirradiate the surface of the substrate 102. Depending on the signal tobe detected, the light source 106 may provide light ranging from thevisible range to the near infrared range. Exemplary light sourcesinclude lasers and light emitting diodes.

The detector 108 is configured to detect light emitted from the surfaceof the substrate 102. In some embodiments, detection is achieved bycolorimetric, fluorescent or luminescent detection. In some embodiments,detection is achieved by imaging such as by photography or by electronicdetectors. Exemplary electronic detectors include photodiodes,charge-coupled device (CCD) detectors, or complementary metal-oxidesemiconductor (CMOS) detectors.

The analog signal from the detector 108 is digitized by ananalog-to-digital converter 110. The digitized signal is processed by amicroprocessor 112 to obtain at least one value or intensity of detectedlight that is store in memory 114 and/or displayed on an optionaldisplay 116.

By using appropriate electronics and software, the system 100 can beprogrammed to know the identity and location of specific substancesbound to the binding agents 110 on the surface of the substrate 102. Theidentity and location of the substances can be correlated with signalsgenerated so that a particular blood grouping can be determined andidentified to the tester. Additionally, statistical software may beincluded so as to combine and formulate the results from the variousrepetitions and/or dilutions of the binding agents 110 provided on thesubstrate 102. In this manner, the signals obtained from a multiplicityof substances may be factored together and a statistically significantresult displayed to the tester.

METHODS

The system 100 may be used to perform antigen typing, antibodyscreening/identification, combined antigen typing and crossmatching.Additionally the system 100 is used for detection of grouping andphenotyping, screening and/or identification of antibodies,cross-matching and direct anti-globulin test.

Referring to FIG. 8, a method 800 for antigen typing and/or antibodyscreening and/or identification will now be described. The method 800,for example, may be executed with the aforementioned system illustratedin FIG. 1.

In exemplary step 810, a sample is applied to a wet or dry substrate 102having one or more binding agents 110 immobilized thereon, wherein theone or more binding agents 110 are capable of binding to one or moresubstances in the sample. In an antigen typing embodiment shown in FIG.2, the sample and substance is patient or donor RBCs treated or nottreated by enzyme and the binding agents 110 immobilized on the surfaceof the substrate 102 are antibodies to red blood cell (RBC) antigens.The RBC sample may be provided by separating whole blood into RBCs andplasma by, for example, centrifugation. The resulting RBCs can be used“as is” or may be diluted. In some embodiments, the RBCs are diluted toabout 0.1 to 50%. In some embodiments, the RBCs are diluted to betweenabout 0.5-20%. In certain embodiments, the RBCs are diluted to betweenabout 0.6 to 5%. In some embodiments, the RBCs are diluted to greaterthan 50%.

In an antibody screening and/or identification embodiment shown in FIG.3, the sample is patient or donor plasma, the binding agents 110immobilized on the surface of the substrate 102 are native or hemolyzedphenotyped RBCs, chemically synthesized polypeptide, natural orsynthesized polysaccharide blood group antigens, or recombinant bloodgroup antigens and the one or more substances are antibodies to RBCantigens, the recombinant red blood cell antigens or red blood cellmembrane extracts.

In an embodiment shown in FIG. 4, the antigen typing embodiment shown inFIG. 2 is combined with the antibody screening and/or identificationembodiment shown in FIG. 3. In this embodiment (e.g., a “combo” assay),a first portion of the substrate has immobilized phenotyped RBC whichmay be native or hemolyzed and a second portion has immobilizedantibodies to RBC antigens.

In an embodiment, one or more samples are applied with one or moremicrofluidic probes. In another embodiment, one microfluidic probe isused for each sample (FIGS. 2-3). Each sample is applied to thesubstrate 102 coated with binding agents 110 in a directionperpendicular to the line of binding agents 110 such that the sample isapplied to each of the binding agents 110 coated on the substrate 102.In yet another embodiment, an array of probes in parallel, probe array900, are connected to the same or different samples (FIGS. 9-10). Theprobe array 900 applies the same or different samples to all the bindingagents 110 at once. For a new sample, the channels in the probe array900 are, for example, rinsed to remove the first sample, the probe array900 are moved together to another set of binding agents 110 and the newsample is applied to the new set of binding agents 110. For each newsample, the process of rinsing and moving the probe array 900 isrepeated. In some embodiments, a plurality of probe arrays 900 are usedto test multiple samples each against multiple binding agent 110 at onetime.

In an embodiment shown in FIG. 11, a microfluidic probe 1100 includes aplurality of processing liquid microchannels. The plurality ofprocessing liquid microchannels may be used to deposit one or moresamples (i.e., the same or different samples) and/or binding agents 110onto the surface of the substrate 102. In some embodiments, themicrofluidic probe includes 2-100 processing liquid microchannels. Inother embodiments, each of the probes in the probe arrays 900 (shown inFIGS. 9-10) includes a plurality of microchannels. In a “combo” assayembodiment, the microfluidic probe 600 shown in FIG. 6 is used todeposit one or more samples onto the embodiment shown in FIG. 4 in whicha first portion of the substrate has immobilized phenotyped RBC, whichmay be native or hemolyzed, and a second portion has immobilizedantibodies to RBC antigens.

In exemplary step 820, unbound material, e.g., red blood cells and/orantibodies, is removed from at least a portion of the substrate 102having immobilized binding agent thereon. The unbound material may beremoved by washing the surface of the substrate 102 with, for example,buffer, water or saline. In an embodiment, a microfluidic probe may beused to remove unbound material concurrent with step 810 by pumping awash solution (e.g., an immersion liquid) through one or more processingliquid microchannels.

In exemplary step 830, substances bound to the one or more bindingagents 110 immobilized on the substrate 102 are detected and thesubstances present in the sample are identified. The absence ofsubstances bound to the binding agents may also be determined. In theantigen typing embodiment, the red color of RBCs bound to the RBCantibodies may be detected visually or spectrophotometrically. The RBCsbound to the RBC antibodies may also be detected by secondary labelingdetection including, for example, colorimetric, fluorescent orchemiluminescent conjugated antibodies. In an antibody screening and/oridentification embodiment, the antibodies bound to the RBC antigens maybe detected by specific secondary labeling detection.

Referring to FIG. 12, a method 1200 for cross-matching will now bedescribed in which a microfluidic probe is used to deposit donor redblood cells and patient plasma. This method tests the compatibility of adonor's RBCs with a patient's plasma. The method 1200, for example, maybe executed with the aforementioned system illustrated in FIG. 1.

In exemplary step 1210, a donor's red blood cells are applied to a wetpre-treated surface of a substrate with the microfluidic probe. Thedonor's red blood cells may be native or hemolyzed. In some embodiments,the donor's red blood cells are also phenotyped. In some embodiments,these RBCs are applied to the surface of the substrate in an immersionliquid to maintain the antigenicity of the red blood cells. In someembodiments, the surface of the substrate is pre-treated with bindingagents such as, for example, lectins, chemical agents or universalanti-RBC antibodies such as, for example, anti-glycophorin A antibody.

In exemplary step 1220, unbound donor red blood cells are removed bywashing the surface of the substrate 102 with, for example, buffer,water or saline. In an embodiment, a microfluidic probe may be used toremove unbound donor red blood cells concurrently with step 1210 bypumping a wash (immersion) solution through one or more processingliquid microchannels.

In exemplary step 1230, a patient plasma sample is deposited on top ofthe donor RBCs applied to the surface of the pre-treated substrate instep 1210. In an embodiment, the same probe as used in step 1210 is usedto deposit the patient plasma. Either the same microchannel or adifferent microchannel as in step 1210 may be used to deposit thepatient plasma. If the same microchannel is used as in step 1210, themicrochannel can be flushed with, for example, buffer between uses or a“slug” of buffer, oil or air may be used to separate the donor RBCs fromthe patient sample. In another embodiment, a different microfluidicprobe is used between this step and step 1210 to prevent crosscontamination.

In exemplary step 1240, unbound antibodies from the patient plasmasample are removed by washing the surface of the substrate 102 with, forexample, buffer, water or saline. In an embodiment, a microfluidic probemay be used to remove unbound antibodies with step 1230 by pumping awash solution through one or more processing liquid microchannels.

In exemplary step 1250, responsive to detecting an antibody bound to thedonor red blood cells, antibody present in the patient plasma isdetected (e.g., by a secondary labeled antibody) and responsive to notdetecting the antibody bound to the donor red blood cells, antibodyabsent in the patient plasma is determined.

In another cross-matching method (e.g., a minor cross-matching method),a microfluidic probe is used to deposit patient RBCs and donor plasma.This method tests the compatibility of a patient's plasma with a donor'sRBCs and is important in the situation where whole blood is transfusedinto a patient rather than just RBCs or where a medically relevantamount of donor plasma remained in the separated RBCs transfused to thepatient. The minor cross-matching method may, for example, be executedwith the aforementioned system illustrated in FIG. 1.

One advantage of the microfluidic probe is its ability to deposit inphysiological immersion liquid which allows for maintaining theantigenicity of the red blood cells. This provides for additionalpossible uses for the probe. In some embodiments, a system for bloodtyping includes a substrate having one or more binding agentsimmobilized in discreet locations, wherein the one or more bindingagents are capable of binding to native or hemolyzed red blood cells; adispenser configured to dispense these native or hemolyzed phenotypedred blood cells onto the substrate and to remove unbound red blood cellsfrom the substrate; a dispenser configured to deposit a patient plasmasample on top of the red blood cells applied to the surface and toremove unbound antibodies and a detector is configured to detectantibodies. The previously described cross-matching is one example.

Antibody screening is another example. Phenotyped RBCs are deposited bythe probe on a pre-treated surface as in the cross-matching assay. Awash is applied and then plasma containing antibodies are deposited andidentified.

EXAMPLES Example 1: Antigen Typing

The objective of this analysis is to identify, by means of specificmonoclonal or polyclonal antibodies, the blood group antigens present atthe surface of red blood cells from donors or from patients (group ABO,RH, Kell, Duffy, Kidd, Lewis, etc.).

In order to demonstrate the possibility of grouping/phenotyping redblood cells with the technology of the invention, the surface of thesubstrate 102 is used to immobilize the anti-red blood cell antibodiesand a microfluidic probe 200 used to dispense patient red blood cells orwhole blood sample and to remove unbound red blood cells. The red colorof the RBCs bound to anti-erythrocytes antibodies is then visuallydetected.

1.1—Material

In this example, the binding agents 110 are anti-erythrocyte antibodies.The surface of the substrate 102 is a polystyrene 96-wells flat bottomplates. Antibodies are deposited with an ink-jet or contact printer asspots on the wells bottoms. Each well contains at least one spot of eachantibody specificity. In this example, antibodies are diluted in PBSbuffer (pH 7.4) at concentration ranging from 10 to 500 μg/mL and boundto the surface of the substrate 102 by passive absorption. Afterdepositing the antibodies on the surface, the substrate is saturated bycontact with PBS supplemented with 1% BSA to prevent non-specificbinding of sample components and subsequently air dried.

In this example, used antibodies are:

Anti-A IgM clone 15750F7 (Bio-Rad),

Anti-D IgG clone BRAD3 (IBGRL),

Anti-K1 IgG clone MID11G4 (Bio-Rad).

1.2—Test Description

In order to demonstrate the feasibility and verify the specificity ofthe grouping according to the technology, each spot is individuallytested. An adequate buffer (processing liquid) is dispensed into thewells in order to cover the whole well surface. The microfluidic probeis then positioned above an antibody spot. In a first step, a suspensionof RBCs or whole blood is flown over the spot to bring RBCs andantibodies into contact. In a second step, the flow is switched to awashing buffer in order to remove unbound RBCs. At the end, the presenceor absence of red blood cells attached to the spotted antibody isdetected visually or spectrophotometrically.

Example 2: Antibody Screening/Identification

In order to demonstrate the possibility of antibody screening andidentification with the technology of the invention, the surface of thesubstrate 102 is used to immobilize native or hemolyzed phenotyped redblood cells via poly-L-lysine (PLL). For this application, themicrofluidic probe 200 is designed to perform heating and sequentialchemistry. The probe is used to deposit patient plasma serum or wholeblood sample, to remove unspecific antibodies and to dispense labeledanti-Fc antibody conjugate to detect bound antibodies.

2.1—Material and Reagents 2.1.1. Sensitization of the Surface of theSubstrate 102 with PLL

In this example, the surface of the substrate 102 is a polystyrene96-wells flat bottom plates. A 25 μg/m1 of PLL of molecular weight 70000-130 000 in PBS, pH 7.4 is dispensed into each well and incubated for18 hours at ambient temperature. At the end of this step, the wells arewashed in PBS pH 7.4 supplemented with 0.05% Tween-20, and then used toimmobilize the cells.

2.1.2. Immobilization of Cells on the Surface

In this example, the binding agents 110 are native or hemolyzedphenotyped red blood cells. Cells are deposited with an ink-jet orcontact printer as spots on the PLL-coated well bottoms. Each wellcontains at least one spot of each phenotype. In this example, 20 to 50%cell suspensions in buffer supplemented with a preservative component.After deposition, the substrate is washed to remove unbound cells andthen saturated by contact with PBS supplemented with 1% BSA and 1 Mdextrose to prevent non-specific binding of sample components and cellspreservation. After an overnight incubation, the saturation buffer isremoved and the surface is air dried.

In this example, used binding agents are three native or hemolyzedphenotyped red blood cells typically used for antibody screening.

2.2. Test Description

Each spot of cells is individually tested. An adequate buffer(processing liquid) is dispensed into the wells in order to cover thewhole well surface. The microfluidic probe is then positioned above aspot. In a first step, the patient plasma serum or whole blood is flownover the spot to bring the sample and RBCs into contact. The probe isset up to heat the reaction area at 37° C. In a second step, thesequential process is applied: washing in order to remove unspecificantibodies, dispensing of labeled anti-Fc antibody conjugate and a finalwashing to remove unbound labeled anti-globulin antibody. At the end,the presence or absence of antibody attached to native or hemolyzedphenotyped red blood cells is detected by colorimetric, fluorescent orluminescent.

Example 3: Cross-Matching

In order to demonstrate the possibility of performing cross-matchingwith the technology of the invention, the microfluidic probe 200 is usedto perform all steps from immobilization of donor red blood cells viapoly-L-lysine (PLL) to final reaction detection. This microfluidic probe200 is designed to perform heating and sequential chemistry. The probeis also used to deposit patient plasma serum or whole blood sample andto remove unspecific antibodies. A labeled anti-Fc antibody conjugate isused to detect the bound antibodies.

3.1—Material and Reagents 3.1.1. Sensitization of the Surface of theSubstrate 102 with PLL

In this example, the surface of the substrate 102 is a polystyrene96-wells flat bottom plates. A 25 μg/ml of PLL of molecular weight 70000-130 000 in PBS, pH 7.4 is dispensed into each well and incubated for18 hours at ambient temperature. At the end of this step, the wells arewashed in PBS pH 7.4 supplemented with 0.05% Tween-20, and then used toimmobilize the cells.

3.1.2. Test Description

An adequate buffer (processing liquid) is dispensed into the PLL-coatedwells in order to cover the whole well surface. The microfluidic probe200 is then positioned above the surface and the sequential process isapplied: deposition of prewashed donor red blood cells, washing step toremove unbound cells, flowing of the patient plasma serum or whole bloodat 37° C., washing to remove unspecific antibodies, dispensing oflabeled anti-Fc antibody conjugate and a final washing to remove unboundlabeled anti-globulin antibody. At the end, the presence or absence ofantibody attached to donor red blood cells is detected by colorimetric,fluorescent or luminescent.

Example 4: Direct Antiglobulin Test

The objective of this analysis is to identify, by means of specificmonoclonal or polyclonal antibodies, IgGs and/or C3d complement fractioncoated on in vivo sensitized RBCs.

In order to demonstrate the possibility to detect sensitized RBCs withthe technology of the invention, the surface of the substrate 102 isused to immobilize the anti-IgGs and anti-C3d antibodies. A microfluidicprobe 200 is used to dispense prewashed patient red blood cells and toremove unbound red blood cells. The red color of the RBCs bound tospecific antibodies is then visually detected.

4.1—Material

In this example, the binding agents 110 are anti-IgGs and anti-C3dantibodies. The surface of the substrate 102 is a polystyrene 96-wellsflat bottom plates. Antibodies are deposited with an ink-jet or contactprinter as spots on the well bottoms. Each well contains at least onespot of each antibody specificity. In this example, antibodies arediluted in PBS buffer (pH 7.4) at concentration ranging from 10 to 500μg/mL and bound to the surface of the substrate 102 by passiveabsorption. After depositing the antibodies on the surface, thesubstrate is saturated by contact with PBS supplemented with 1% BSA toprevent non-specific binding of sample components and subsequently airdried.

In this example, used antibodies are:

Polyclonal rabbit anti-human-IgG (Bio-Rad),

Anti-C3d IgG clone 053A714 (Bio-Rad).

4.2—Test Description

In order to demonstrate the feasibility and verify the specificity ofthe test, the reactions are carried out in a unitary manner. In thiscase, each spot is individually tested. An adequate buffer (processingliquid) is dispensed into the wells in order to cover the whole wellsurface. The microfluidic probe is then positioned above an antibodyspot. In a first step, a suspension of RBCs is flown over the spot tobring RBCs and antibodies into contact. In a second step, the flow isswitched to a washing buffer in order to remove unbound RBCs. At theend, the presence or absence of red blood cells attached to the spottedantibody is detected visually or spectrophotometrically.

Example 5: Antigen Typing—Singleplex and Multiplex Grouping/Phenotyping

The objective of this analysis was to identify, by using specificmonoclonal or polyclonal antibodies, the blood group antigens present atthe surface of red blood cells from donors or from patients (group ABO,RH, Kell, Duffy, Kidd, Lewis, etc.).

To demonstrate the possibility of phenotyping/grouping red blood cellswith the technology of the invention, an anti-red blood cell antibodywas immobilized on the surface of the substrate and a microfluidic probewas used to dispense patient red blood cells concurrent with removingunbound red blood cells. The red color of the red blood cells bound toanti-erythrocytes antibodies was then visually detected, and was used todetermine the antigenic specificities.

A. Singleplex Grouping of A-Positive Red Blood Cells Materials

In this example, the binding agent was anti-red blood cell antibody, andmore particularly a murine IgM anti-A mAb (Bio-Rad clone 15750F7). Forthis experiment and all the subsequent experiments, the substrate was apolystyrene slide (TED PELLA, INC.; product #260225). Antibody wasdeposited with an ink-jet printer as rows of spots on the slide. Eachspot was clearly identified by X,Y coordinates. The spot size was about250 μm in diameter. The spots were aligned with each other and werespaced apart by about 50-60 μm. The purified anti-A IgM antibody wasdiluted in PBS buffer (pH 7.4) at a concentration ranging from 10 to 500μg/mL and was bound to the surface of the substrate 102 by passiveabsorption. After depositing the antibody on the surface, the substratewas treated with 1% BSA in PBS to prevent non-specific binding of samplecomponents. The slides thus prepared were air dried and were stored at4° C. until use. The microfluidic probe used in this and subsequentexamples was a probe with 4 channels, each having dimensions of 100μm×100 μm. To obtain an adequate hydrodynamic flow confinement, channel2 was used to dispense sample and channels 1 and 3 were used to aspiratesample. Red blood cell suspensions having different phenotypes (Apositive and O positive red blood cells) were used as samples.

Method

To demonstrate the feasibility and verify the specificity as well as thereproducibility of the grouping according to the technology, each spotwas tested one after another with the same red blood cell solution(e.g., two A-positive red blood cells as well as two A-negative redblood cells (O red blood cells)). In this example, the red blood cellswere washed in 0.9% isotonic saline solution and suspended at 50% inphysiologic water. With the channel 2 of the microfluidic probe, 2 μl ofthe diluted red blood cell suspension was aspirated at 1.6 μl/min. Towet the slide, sufficient buffer (processing liquid) was dispensed ontothe slide to cover the whole surface. The microfluidic probe was thenpositioned above the slide and hydrodynamic flow confinement was thenset up. When the hydrodynamic flow confinement was stabilized, themovement of the microfluidic probe was programmed to move at a rate of0.02 mm/s and to follow a straight line passing through the alignedspots. During movement of the probe, the red blood cells dispensed wereeither in contact with the saturated surface of the substrate 102 orwere in contact with the spotted antibody. Red blood cells having thecorrect antigenic specificity bound immediately to the immobilizedantibodies. Due to the continuous deposition and aspiration of cells andbuffer processing fluid, the unbound red blood cells were removedconcurrently with the binding of red blood cells. Afterdeposition/aspiration of the red blood cells, the presence or absence ofred blood cells attached to the spotted antibody was detected by cameraimage capture. Knowing the position of each spot on the substrate, itwas possible to confirm if the antigens were present at the surface ofred blood cells being tested, and thus to identify the blood groupspecificity of the red blood cells being tested.

To determine if antigens were present at the surface of A-positive andA-negative RBCs, two A-positive red blood cells and two A-negative redblood cells were tested by depositing the RBCs on 20 spots. The testresults for four of the 20 spots having A-positive red blood cells boundare shown in FIG. 13A. A close up view of the fourth spot is shown inFIG. 13B. The A-positive red blood cells bound strongly to the entirespot surface, whereas the A-negative red blood cells did not bind at all(not shown). These results demonstrate that the binding observed isspecific: the red blood cell binding occurs only when anantigen-antibody pair is involved. The results also demonstrate that theA-positive red blood cells can be clearly distinguished from theA-negative red blood cells such that the A antigen at the surface of redblood cells can be identified. Additionally, these results show that themicrofluidic probe can be used in a singleplex antigen typing method inwhich a microfluidic probe is used to apply RBCs to anti-red blood cellsantibodies on a solid substrate while concurrently removing unboundRBCs.

The applicant also found that when red blood cells with a lower antigendensity were evaluated, the spot surface covered by the red blood cellswas less dense.

B. Multiplex Grouping of A and D Positive Red Blood Cells

In this example, the same aliquot of red blood cells (and therefore lesssample) was used to react separately with an immobilized murine IgManti-A monoclonal antibody (mAb) as well as immobilized human IgG anti-DmAb.

Materials

The binding agents were anti-red blood cell antibodies: murine IgManti-A (clone 157 50 F7) and human IgG anti-D mAbs (clone Brad3).Antibodies were deposited manually as spots on the polystyrene slide.Each spot was clearly identified by the X,Y coordinates. In this case,the spot size was about 1.5 mm in diameter. The spots with the sameantibody specificity were aligned with each other and were spaced apartfrom each other by about 200 μm. The antibodies used had been purifiedand diluted in PBS buffer (pH 7.4) at a concentration ranging from 10 to500 μg/mL. The diluted antibodies were bound to the surface of thesubstrate by passive absorption. After depositing the antibodies on thesurface, the substrate was saturated with PBS supplemented with 1% BSAto prevent non-specific binding of sample components. The slides wereair dried and stored at 4° C. until use. The conditions used to obtainan adequate confinement were as follows: channel 1: aspirate, channel 2:dispense, and channel 3: aspirate. Red blood cell suspensions havingdifferent A and D phenotypes (A+, A−, O+ and O−) were used as samples.

Method

To demonstrate the feasibility and verify the specificity ofgrouping/phenotyping using the microfluidic probe technology, each spotwas tested one after another with the same red blood cell solution. Inthis example, the red blood cells were first washed in 0.9% isotonicsaline solution and were suspended at 50% in physiologic water. 1.5 μlof red blood cell suspension was aspirated at 1.5 μl/min. To wet theslide, sufficient PBS buffer (processing liquid) was dispensed onto theslide to cover the whole surface. The microfluidic probe was positionedabove the slide and hydrodynamic flow confinement was then set up. Whenhydrodynamic flow confinement was stabilized, the movement of themicrofluidic probe following the X-axis or Y-axis was programmed at 0.02mm/s so that a straight line passing through the aligned spots wasdrawn. During movement of the probe, the red blood cells dispensed wereeither in contact with the saturated surface of the substrate or were incontact with one of the spotted antibodies. Red blood cells having thecorrect antigenic specificity bound immediately to the immobilizedantibodies. Due to the continuous deposition and aspiration of cells andbuffer processing fluid, the unbound red blood cells were removedconcurrent with binding of red blood cells. After deposition/aspirationof the red blood cells, the presence or absence of red blood cellsattached to the spotted antibody was detected by camera image capture.Knowing the position of each specific antibody on the substrate, it waspossible to identify which antigens were present at the surface of redblood cells being tested, and thus to identify the blood groupspecificity of the red blood cells being tested.

A-positive red blood cells (A+, A−) and D-positive red blood cells (A+,O+), as well as A-negative (O− and O+) and D-negative red blood cells(O− and A−) were used as samples and were deposited in a line on 2 spotseach. The A-positive red blood cells bound strongly to the scannedregion of the spot surface at which the anti-A mAb was immobilized (FIG.14A), whereas the A-negative red blood cells did not bind at all (FIG.14B). The D-positive red blood cells also bound strongly to the scannedregion of the spot surface at which the anti-D mAb was immobilized (FIG.14C), whereas the D-negative red blood cells did not bind at all (FIG.14D). These results demonstrate that the binding observed was specific:the spot/red blood cell binding occurs only when an antigen-antibodypair is involved. These results also demonstrate the feasibility oftwo-parameter multiplexed grouping/phenotyping of red blood cells usingthe microfluidic probe technology of the invention. Additionally, theseresults show that the microfluidic probe can be used in a multiplexantigen typing method in which a microfluidic probe is used to applyRBCs to anti-red blood cells antibodies on a solid substrate whileconcurrently removing unbound RBCs. These results also show that thesame sample can be used to carry out the multiplexing reaction, i.e.,the same sample can be applied to all the spots.

Example 6: Phenotyping of Direct Coombs Positive Red Blood Cells: DirectAntiglobulin Test

The objective of this analysis was to identify, by using specificmonoclonal or polyclonal antibodies, human IgGs and/or C3d complementfraction adsorbed on in vivo sensitized red blood cells.

Here, to demonstrate the possibility of detecting sensitized red bloodcells with the technology of the invention, an anti-human globulin mAb(a murine IgG mAb) was immobilized on the surface of the substrate. Themicrofluidic probe was used to dispense human IgG sensitized red bloodcells and to remove unbound red blood cells. The red color of the redblood cells bound to the specific antibody was then visually detected bycamera image capture.

Materials

In this example, the binding agent was an anti-human globulin antibody(a murine IgG mAb). The entire surface of a polystyrene slide wasmanually functionalized with the antibody. The purified antibody wasdiluted in PBS buffer (pH 7.4) at concentration ranging from 10 to 500μg/mL and was bound to the surface of the polystyrene slide by passiveabsorption. After depositing the antibody on the surface of the slide,the slide was saturated by contact with PBS supplemented with 1% BSA toprevent non-specific binding of sample components. These slides weredried and stored at 4° C. until use. The conditions used to obtain anadequate confinement were as follows: channel 1: aspirate, channel 2:dispense, and channel 3: aspirate. Sensitized red blood cellssuspensions as well as native red blood cells suspensions were used assamples.

Method

To mimic in vivo sensitized red blood cells, human anti-D IgG was usedto sensitize red blood cells. D-positive red blood cells that had beenwashed with 0.9% isotonic saline solution were suspended at 2% inphysiologic water. In parallel, a solution of human anti-D mAb at 20μg/ml was prepared. The washed D-positive RBC solution was mixed withthe solution of human anti-D mAb and was incubated for 45 min at 37° C.To remove the unbound antibody, the anti-D sensitized RBCs were washedwith 0.9% isotonic saline solution and were suspended at 10%. The anti-Dsensitized RBCs were tested in Direct Coombs Cards (IgG+C3d), and astrong positive reaction was obtained. 2 μl of the sensitized RBCsuspension was then aspirated at 1.8 μl/min with channel 2 of themicrofluidic probe. The entire surface of the slide was wet with PBS.The probe was then positioned above the slide. After stabilizing themicrofluidic probe flow confinement, the microfluidic probe wasprogrammed to follow a straight line along the X-axis at a velocity of0.02 mm/s.

Anti-D sensitized red blood cells and the same red blood cells withoutany sensitization (i.e., native RBCs) were deposited with themicrofluidic probe on the slide having a binding agent of anti-humanglobulin antibody. Concurrent with the application of the sample to thebinding agent, unbound material was removed by the probe. The presenceor absence of red blood cells attached to the antibody was detected bycamera image capture. Anti-D sensitized RBCs should bind to theanti-human globulin antibody, whereas RBCs that did not undergosensitization should not bind to the anti-human globulin antibody.

The results show that only the anti-D sensitized red blood cells boundstrongly to the anti-human globulin mAb across the entire scanningregion (FIG. 15), whereas the native red blood cells did not bind at all(not shown). These results demonstrate that the binding observed isspecific. Additionally, these results show that the microfluidic probecan be used in a direct antiglobulin test in which a microfluidic probeis used to apply human IgG sensitized red blood cells to anti-humanglobulin monoclonal antibodies on a solid substrate while concurrentlyremoving unbound RBCs.

Example 7A: Antibody Screening/Identification

The screening for atypical anti-red blood cell antibodies is required toallow compatible transfusion between a donor and a recipient. Thepurpose is to verify that the recipient's plasma does not containantibodies directed against the donor red blood cells which must betransfused. The screening needs to use several red blood cellscharacterized by the distribution of blood group antigens on theirsurface. Such screening is as follows: red blood cells whose phenotypeis known are incubated with the serum or plasma sample to be tested. Ifpresent, specific antibodies bind to the surface of the red blood cellsand are detected with a reagent containing an anti-human globulinantibody. By using panels of red blood cells which have or do not havevarious antigens, it is then possible to determine the specificity ofthe antibodies present in the sample. To demonstrate the possibility ofantibody screening and identification with the technology of theinvention, the surface of the substrate was used to immobilize native orhemolyzed phenotyped red blood cells via a universal antibody. Themicrofluidic probe was then used to dispense anti-D monoclonal antibodyto mimic patient plasma. While dispensing anti-D monoclonal antibody,the probe concurrently removed non-specifically bound material. Theprobe was also used to dispense 10 μg/ml phycoerythrin-labeledanti-human globulin antibody (secondary antibody) to detect bound anti-Dmonoclonal antibody.

Materials

In this example, the entire surface of polystyrene slides was manuallyfunctionalized with an universal anti-red blood cells antibody. Theanti-red blood cell antibody used was purified and diluted in PBS buffer(pH 7.4) at concentrations of 100 μg/mL and were bound to the surface ofthe slides by passive absorption. The slides were then saturated bycontact with PBS supplemented with 1% BSA to prevent non-specificbinding of sample components. After air drying, the slides were storedat 4° C. until use. Phenotyped red blood cells were washed with 0.9%isotonic saline solution, and then were suspended at 0.5%. This redblood cells suspension was then incubated with a slide during 20 min at37° C. in a wet room. Then, the slide was washed with a 0.9% isotonicsaline solution to remove unbound red blood cells. The microfluidicprobe was then used to deposit a sample mixture of 4 μg/ml monoclonalanti-D mAb (primary antibody) and 10 μg/ml phycoerythrin-labeledanti-human globulin mAb (secondary antibody) diluted in a low ionicstrength buffer. Because the sample mixture was not detectable withoutany labeling, the microfluidic probe was run in double flow confinementmode which means that the sample mixture was nested inside anothershaped liquid that itself was confined within the immersion liquid(PBS). In this case, the second confinement was carried out with afluorescein solution, which was visible and guaranteed the appropriateconfinement of the sample mixture. With the microfluidic probe, thesample mixture was dispensed with the channel 2 and aspirated with thechannel 3, and the fluorescein solution was dispensed with channel 1 andaspirated with channel 4.

Method

The mixture (3 μl) of the monoclonal anti-D mAb with 10 μg/mlphycoerythrin-labeled anti-human globulin mAb was aspirated at 3.5μl/min with channel 2 of the microfluidic probe. An adequate amount ofPBS buffer (processing liquid) was dispensed to wet the whole surface ofthe slide. The microfluidic probe was then positioned above the slideand the double flow confinement mode was set up. After stabilizing thedouble flow confinement, the probe was set up to remain between 30 s to180 s at the same location. Sample application and removal of unboundmaterial was concurrent. The presence or absence of antibody labeled bythe anti-human globulin mAb and attached to the native red blood cellswas detected by reading the fluorescence with a fluorescence microarrayanalyzer SensoSpot (Sensovation AG, Radolfzell, GE).

As shown in FIG. 16, anti-D mAb bound to the D-positive RBCs no matterhow long the probe remained at the same location. Similar results wereobtained when the monoclonal anti-D mAb and the labeled anti-humanglobulin mAb were applied separately to the D-positive RBCs. Thisexperiment demonstrates that the microfluidic probe can be used in anantibody screening/identification method in which sample is appliedconcurrent with removal of unbound material.

Example 7B: Reverse ABO Grouping Test

The objective of this analysis was to show the presence or absence, in ablood sample, of natural antibodies directed against the A and/or Bblood group antigens. The result of this analysis, combined with thatobtained in a direct test, will make it possible to establish the ABOgroup of the sample. The sample used in the reverse ABO grouping testmay be a serum, plasma or whole blood sample. To demonstrate thepossibility of reverse ABO grouping with the technology of theinvention, the surface of the substrate was used to immobilize nativephenotyped red blood cells via a universal antibody. For thisapplication, the microfluidic probe was used to deposit patient plasmaserum and to remove unbound material.

Materials

As in the previous example, the surface of the entire polystyrene slidewas entirely functionalized with an universal anti-red blood cellantibody. After depositing the universal anti-red blood cell antibodyonto the surface of the slides, the slides were saturated by contactwith PBS supplemented with 1% BSA to prevent non-specific binding ofsample. These slides were air dried and were stored at 4° C. until use.Phenotyped A-positive red blood cells were washed with a 0.9% isotonicsaline solution and were suspended to a final concentration of 0.5%.This red blood cell suspension was then incubated with a slide for 20min at 37° C. in a wet room. Next, the slide was washed with a 0.9%isotonic saline solution to remove unbound red blood cells. Themicrofluidic probe was then used to deposit plasma from a B blood typeperson. Because the plasma was not detectable without any labeling, themicrofluidic probe was again used in double flow confinement mode as inthe previous example.

Method

The plasma sample was aspirated at 3.2 μl/min with the channel 2 of themicrofluidic probe. An adequate buffer (processing liquid) was dispensedonto the slide to wet the whole surface. The microfluidic probe waspositioned above the slide and the double flow confinement mode was thenset up. When the double flow confinement was stabilized, the probe wasset up to remain between 30 s to 180 s at the same location. Again,application of sample and removal of unbound material occurredsimultaneously. The slide was then incubated 15 min at 37° C. in a bathwith a 10 μg /ml phycoerythrin-labeled anti-human H+L Ab. The presenceor absence of plasma antibody labeled by the anti-human H+L Ab and boundto the native red blood cells was detected by reading the fluorescencewith the fluorescence microarray analyzer SensoSpot (Sensovation AG,Radolfzell, GE).

As shown in FIG. 17, anti-D mAb bound to the A-positive RBCs, theintensity of the binding increases with the time where the proberemained at the same location. This experiment demonstrated that amicrofluidic probe can be used in a reverse grouping method in whichpatient plasma is applied to phenotyped red blood cells concurrent withremoving unbound plasma material.

Example 8: Cross-Match

One objective of this analysis was to be sure that in the context of atransfusion of one or more blood cell concentrates from donors to arecipient, there was complete donor-recipient compatibility. Anotherobjective was to demonstrate an incompatibility linked to the presenceof antibodies in the recipient's plasma, directed against blood groupstructures carried by the red blood cells of the donor. The microfluidicprobe was used to perform the immobilization of donor red blood cellsvia a universal antibody, to deposit the patient plasma, and to removenon-specifically bound patient plasma material. Detection of thepresence or absence of the plasma antibodies bound to the red bloodcells was carried out with a labeled anti-human globulin Ab.

Materials

The surface of the entire polystyrene slide was entirely functionalizedwith an universal anti-red blood cell antibody as in example 7A. Afterdepositing the universal anti-red blood cell antibody on the surface ofthe slides, the slides were saturated by contact with PBS supplementedwith 1% BSA to prevent non-specific binding of sample components. Theslides were air dried and were stored at 4° C. until use. A+donor redblood cells were washed with 0.9% isotonic saline solution and weresuspended at a concentration of 50%. To dispense the A+ donor RBCs, themicrofluidic probe was operated in hydrodynamic flow confinement mode asfollows: channel 1: aspirate, channel 2: dispense, and channel 3:aspirate. Then a double confinement mode was used to dispense A+ or O+patient plasma as follows: plasma was dispensed with the channel 2 andaspirated with channel 3 and fluorescein solution was dispensed withchannel 1 and aspirated with channel 4.

Method

In this example, 2.5 μl of the A+ donor red blood cell suspension(diluted suspension at 50%) was aspirated at 1.5 μl/min with themicrofluidic probe. PBS buffer (processing liquid) was dispensed intothe slide to wet the whole surface. The microfluidic probe was thenpositioned above the slide and the flow confinement was then set up.When flow confinement was stabilized, the movement of the microfluidicprobe was programmed at 0.03 mm/s to draw a straight line along theX-axis. The length of the line was about 12 mm. During movement of theprobe, the A+ donor red blood cells were immediately bound to theuniversal anti-red blood cell antibody bound to the surface of theslide. Due to the continuous flow, as red blood cells were dispensed,the unbound red blood cells were concurrently removed. The microfluidicprobe was then used to deposit the A+ or O+ patient plasma in dual flowconfinement mode as previously described. With the microfluidic probe, 2μl of the plasma was aspirated at 3 μl/min. The microfluidic probe wasset up to remain at the same location for 60 seconds with the A+ plasmaand for 30 or 60 seconds with the O+ plasma. Concurrent with applyingplasma to the previously applied RBCs, unbound material was removed withthe probe. The slide was then incubated 15 min at 37° C. in a bath with10 μg /ml phycoerythrin-labeled anti-human globulin Ab. Finally, thepresence or absence of antibody labeled by the phycoerythrin-labeledanti-human globulin Ab and bound to the native red blood cells wasdetected by reading the fluorescence with the fluorescence microarrayanalyzer SensoSpot (Sensovation AG, Radolfzell, GE).

As shown in FIGS. 18A and 18B, the A+ plasma did not bind to the A+ redblood cells (e.g., only a faint spot was detected). However, binding wasobserved with the O+ plasma, even at an incubation time of 30 seconds.This experiment demonstrated that the microfluidic probe can be used ina cross-matching method in which donor plasma is applied to immobilizedred blood cells concurrent with removing unbound plasma material.

As used in this specification and in the claims appended hereto (and inthe items herein), the term “comprise” and variations thereof such as“comprises” and “comprising,” when preceding the recitation of a step oran element, are intended to mean that the addition of further steps orelements is optional and not excluded. All patents, patent applications,and other published reference materials cited in this specification arehereby incorporated herein by reference in their entirety. Anydiscrepancy between any reference material cited herein or any prior artin general and an explicit teaching of this specification is intended tobe resolved in favor of the teaching in this specification. Thisincludes any discrepancy between an art-understood definition of a wordor phrase and a definition explicitly provided in this specification ofthe same word or phrase.

The text of U.S. patent application Ser. No. 13/881,989 is incorporatedhereinafter.

We claim:
 1. A system comprising: a substrate having a binding agentimmobilized in discreet locations, wherein the binding agent is capableof binding to a substance in a sample; a dispenser configured tosimultaneously dispense the sample onto the substrate and to removeunbound material from the substrate; a light source configured toilluminate the substrate; and a detector configured to detect thepresence or absence of the substance bound to the binding agent.
 2. Thesystem of claim 1, wherein the dispenser is a microfluidic probe havinga plurality of microchannels.
 3. A method of cross-matching comprising:applying donor red blood cells to a surface of a substrate having abinding agent immobilized thereon, wherein the binding agent is capableof binding to the donor red blood cells; removing unbound donor redblood cells from at least a portion of the substrate having immobilizedbinding agent; wherein the applying the donor red blood cells to thesurface of the substrate step is concurrent with the removing unbounddonor red blood cells from at least a portion of the substrate step;depositing patient plasma on top of the donor red blood cells; andremoving an unbound portion of the patient plasma; wherein thedepositing a patient plasma step is concurrent with the removing unboundportion of the patient plasma step; responsive to detecting an antibodybound to the donor red blood cells, determining that the antibody ispresent in the patient plasma; and responsive to not detecting theantibody bound to the donor red blood cells, determining that theantibody is absent in the patient plasma.
 4. The method of claim 3,wherein the applying donor red blood cells, removing unbound donor redblood cells, depositing patient plasma and removing the unbound portionof patient plasma steps are performed with a microfluidic probe.
 5. Asystem for cross-matching comprising: a substrate having donor red bloodcells immobilized in discreet locations thereon; a dispenser configuredto simultaneously dispense donor red blood cells or patient plasma ontothe substrate and to remove unbound donor red blood cells or an unboundportion of the patient plasma from the substrate; a light sourceconfigured to illuminate the substrate; and a detector configured todetect the presence or absence of antibodies bound to the donor redblood cells.